Drivers of motor vehicles are informed of risks or prevailing legal provisions by means of traffic signs. For example, existing speed limits, restrictions on passing or street conditions are indicated with the aid of traffic signs. Also a traffic routing is represented by traffic signs, such as e.g. existence of a one-way street or a dead-end street as well as a prohibition of access into a defined street. Recently, motor vehicles are equipped with an increasing number of assistance systems to make the operation of motor vehicles easier for the drivers. For example assistance systems are known, which allow the detection of traffic signs. For this purpose, a region in front of the vehicle is recorded by means of a camera and a traffic sign shown there is determined.
To determine the traffic sign the produced image is verified as to whether it contains a known pattern, which represents a reproduction of the traffic sign. Round traffic signs here differ merely in the diameter, which can be adapted by means of a suitable scaling of the reproduction of the traffic sign. Rectangular traffic signs are a challenge, as they usually differ comparably distinctly in their height to width ratio. Thus, essentially quadratic traffic signs exist, but also traffic signs, with their width being 1.5 times their height. Also traffic signs are country-specific, so that within the assistance system a plurality of different traffic sign forms must be stored to guarantee proper operation. This is relatively elaborate and memory intensive.
Moreover, the produced image must be analyzed as to a presence of all stored traffic sign forms. This requires comparably high computing power, so that an evaluation of the detected image essentially cannot be realized in real time or only by means of a comparably cost-intensive computing unit. Therefore, not all images are detected, which would be detectable by means of a camera of the assistance system. As a consequence it is possible that a traffic sign is not detected by means of the assistance system and hence the driver of the motor vehicle is not informed about its presence.